United Nations (CNN) -- The U.N. Security Council on Monday gave nations new powers to pursue pirates into the waters off Somalia, an effort to combat a new spate of hijackings off the Horn of Africa.

The Spanish-registered Playa de Bakio was seized by pirates off Somalia in April.

The unanimous resolution calls on U.N. members to use "all necessary means to repress acts of piracy and armed robbery," and authorizes warships to chase pirates into Somali territorial waters if necessary.

"This allows and calls on the member states to assist the authorities in Somalia to combat piracy off the coast of Somalia," said Zalmay Khalilzad, the U.S. ambassador to the United Nations.

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A French-led squadron, which includes U.S. and German ships, is currently patrolling the Somali coast. Still, three European freighters were hijacked last week in the Gulf of Aden, which connects the Red Sea and the Arabian Sea off the Horn of Africa.

The Gulf of Aden in particular has become a treacherous stretch for shipping in recent months, with more than two dozen pirate attacks reported since the beginning of 2008, according to the International Maritime Bureau.

Nine of those have been successful hijackings, the bureau said.

Cyrus Mody of the bureau told CNN last week that Somali pirates appear to take ships "purely for financial gain." In seven hijackings this year, most were resolved with a ransom payment, Mody said, adding that the pirates in Somalia typically treat the crews on the hijacked ships well.

It is difficult to tell whether a single group is responsible for the hijackings, given that there are at least four pirate groups in the country, he said.

Somalia's U.N.-backed transitional government has said it would welcome international assistance in battling piracy, which the Security Council has now declared an aggravating factor in the situation there.

Somali leaders are struggling to restore order after about 15 years of near-anarchy, and are also battling an Islamic insurgency.

Meanwhile, the international flotilla first dispatched to prevent the spread of the al Qaeda terrorist movement has taken an increasingly prominent role in battling piracy.

In April, French commandos captured six pirates who had just released the crew of a hijacked luxury yacht and were trying to escape with the ransom. The gang have been taken to France for trial.

The resolution was backed by the United States, France, Britain and Panama.